Well.. a million thanks for that. Quite a cool history lesson as well. So
now I'm looking for an SEA tuner... LOL...

Listen, that all makes perfect sense but just to clarify, a.) now I know why
that triton did so poorly when tested. We calc'd 1/2 wavelength for the
longwire, and b.) Again, for continuity and clarity of this thread for
future surfers...... what then, considering our discussed auto-tuners, would
be the optimal length for a longwire that would be used for amateur/MARS,
3-30MHz?
Pick 1/2wavelength on say 2.8Mhz and just cut it? Or calc 1/2wavelength on
the lowest and add 5% or some arbitrary odd number??
Which plan will offer the least chance of dropping a 1/2wl further up the
band on a desired frequency?
thanks,
Woody


"Bruce in Alaska" wrote in message
...
In article imYki.1884$YH3.394@trnddc08, "Woody"
wrote:

Yeah, I noticed the same thing with the motorola triton, another
antique....
maybe the newer ones aren't so quirky?
W

Interesting you should notice that. The original Binary Switch Lump
Constant Autotuners were those designed for the Triton Series MF/HF
SSB Radio's, from Motorola, by Bill Schilb. When he left Motorola
and came west, to Northern Radio in Seattle, he brought that technology
with him and introduced it to the MF/HF Marine Market. First at Northern,
which never did anything with it, and then on to SEA, thru the
ex-Northern Engineering Team, that followed Dick Stephens, from
Northern, to SEA, as Northern was sinking into oblivian. The first
Marine Product with this technology, was the SEA-1601 Autotuner, Designed
by Bill Forgey, and Mark Johnson. A sucsession of improvments followed
culminating in the SEA-1612B Autotuner. This is the model that SGC
copied, for their original product, including the Firmware that still had
the SEA Copyright, compiled in the code. Most of the later Binary
Switched Autotuners are, either Copied, or Reverse Engineered,
adaptations of the SEA1612B System. All these tuners NEED a Low
Impedance RF Ground to work against, as well as a Longwire who's length
is SPECIFICALLY set up to put the 1/2 Wavelength Point in a non used
portion of the Spectrum. They will NOT tune within 2% of the Natural
1/2 Wavelenth point of the Longwire connected, where Antenna Impedances
near Infinity.

There has been considerable work done, over the years, on making this
type tuner, drive Balanced Antennas. Some have used a 4:1 Balun,
directly across the tuner Output, with limited sucess. Some have
decoupled the Tuner from it's Coaxial Feedline, Power, and Tuner
Indicator Lines, by running them thru a Bifilar Wound Torroid at
the Tuner end, and then putting the tuner in the Center of a Dipole
cut for the Lowest Desired Frequency of the System. This type has proved
a better system than the Balun, but I have used both at Limited Coast
Stations thruout Alaska, and most are still in operation today.
G & L Marine Radio in Seattle, once designed an SEA-1612B based Autotuner
that had two Tuner boards, one for each side of the Balanced Antenna,
that ran off a single MCPU and Detector System, and just latched
the same Data into both boards. I never actually heard how well Don Sr.
got it to work, but always thought that it was an interesting concept.

Bruce in alaska
--
add a 2 before @

In article t3ali.3392$Y_3.570@trnddc04, Woody wrote:

Well.. a million thanks for that. Quite a cool history lesson as well. So
now I'm looking for an SEA tuner... LOL...

Listen, that all makes perfect sense but just to clarify, a.) now I know why
that triton did so poorly when tested. We calc'd 1/2 wavelength for the
longwire, and b.) Again, for continuity and clarity of this thread for
future surfers...... what then, considering our discussed auto-tuners, would
be the optimal length for a longwire that would be used for amateur/MARS,
3-30MHz?
Pick 1/2wavelength on say 2.8Mhz and just cut it? Or calc 1/2wavelength on
the lowest and add 5% or some arbitrary odd number??
Which plan will offer the least chance of dropping a 1/2wl further up the
band on a desired frequency?

I think you'll need to run a a simple calculation, based on the
frequencies you actually want to use.

What you'll want, is a wire whose length is not particularly close to
any multiple of 1/2 wavelength, on any frequency you want to use. A
wire which would match easily on 80 meters (e.g. 1/4 wavelength long)
would be a bad choice if you want to work on 40 meters as well, as
it'd be 1/2 wavelength long.

A simple program or spreadsheet ought to be able to do the necessary
calculations... try every wire length from 66 feet to 132 feet and see
if you can find a length which is a comfortable percentage away from
an even multiple of 1/2 wavelength on each frequency. Or,
alternatively, iterate through each frequency, calculate the
1/2-wavelength multiples, and "blacklist" every possible length which
is too close to these multiples.

For what it's worth, SGC sells a longwire antenna 60' in length, which
they say works well on both lower and higher HF bands. It might or
might not be a good choice for MARS frequencies.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

(Dave Platt) wrote in
news
....

I think you'll need to run a a simple calculation, based on the
frequencies you actually want to use.

What you'll want, is a wire whose length is not particularly close to
any multiple of 1/2 wavelength, on any frequency you want to use. A
wire which would match easily on 80 meters (e.g. 1/4 wavelength long)
would be a bad choice if you want to work on 40 meters as well, as
it'd be 1/2 wavelength long.

A simple program or spreadsheet ought to be able to do the necessary
calculations... try every wire length from 66 feet to 132 feet and see
if you can find a length which is a comfortable percentage away from
an even multiple of 1/2 wavelength on each frequency. Or,

You probably mean't any integral multiple of a half wave.

alternatively, iterate through each frequency, calculate the
1/2-wavelength multiples, and "blacklist" every possible length which
is too close to these multiples.

I have done just that, and searched for "sweet" wire lengths that aren't
within say 5% of band edge for all HF bands. It sounds like a solution to
the problem doesn't it. (5% implies that you have a pretty determinate
scenario, which is a big assumption. IIRC 10%+ will not give a practical
result on the higher bands.)

Problem is that it probably unecessarily constrains the solution.

The input impedance and the feed point voltage of an end fed wire at its
higher parallel resonances falls, so that whilst you might want to avoid
the first such resonance, the impedance (and feed point voltage) at the
third or higher resonance might well be low enough to not worry about it.

To demonstrate that life isn't simple, the antenna efficiency (Rr/Rtot at
the feedpoint) improves closer to those parallel resonances that everyone
wants to avoid.

Owen

Hi Owen. 5% was just a number picked out at random by me for clarification
of my question.
So you wouldn't want to share your 'sweet' findings, would you??
thanks!
W


"Owen Duffy" wrote in message
...




I have done just that, and searched for "sweet" wire lengths that aren't
within say 5% of band edge for all HF bands. It sounds like a solution to
the problem doesn't it. (5% implies that you have a pretty determinate
scenario, which is a big assumption. IIRC 10%+ will not give a practical
result on the higher bands.)
Owen

"Woody" wrote in news:hYdli.29709$BT3.8034@trnddc06:

Hi Owen. 5% was just a number picked out at random by me for
clarification of my question.
So you wouldn't want to share your 'sweet' findings, would you??
thanks!

W,

I have had a quick look for the spreadsheet and Perl scripts, but haven't
found them. I am sure I have them, but haven't filed them in an ordered
way apparently, I think that technically is lost... or galloping
senility.

The reason I didn't publish them as is at the time is is that they are an
incomplete picture.

Have a look at the article at
http://www.vk1od.net/InvertedL/InvertedL.htm which describes an InvertedL
at approximately one of those "sweet" lengths (~26m). In fact, the length
was juggled to avoid excessive feedpoint voltage on all bands.

Another of the "sweet" lengths is half that at 13m, and the voltage plot
is rougly scaled proportionately in frequency.

You will see from Fig 1 that the voltage peaks at higher frequency
parallel resonances are less an issue than the first and second
resonances (you can't see from the graphs, but ~10kV and 3kV
respectively).

Of course, none of this discussion addresses the pattern issues at the
higher frequencies.

As far as the earth system goes, it impacts efficiency of the system. It
is my view that the earth only needs to be good enough that its loss is
an acceptably low portion of the transmitter power. The shorter the
radiator in wavelengths, the lower its Rr and therefore the lower the
earth resistance for comparable efficiency. If you look at Fig 4 of the
article, you will see that Rr is 100 ohms or greater above 5MHz, so the
loss of an earth system resistance of say 30 ohms is near insignificant,
but at 80m where the length is relatively short, you need a better earth
for good efficiency.

Don't agonise over it too much, and treat the Rules of Thumb as ROT until
you understand the underlying assumptions and caveats.

Owen

W


"Owen Duffy" wrote in message
...




I have done just that, and searched for "sweet" wire lengths that
aren't within say 5% of band edge for all HF bands. It sounds like a
solution to the problem doesn't it. (5% implies that you have a
pretty determinate scenario, which is a big assumption. IIRC 10%+
will not give a practical result on the higher bands.)
Owen

"Woody" wrote in news:hYdli.29709$BT3.8034@trnddc06:

Hi Owen. 5% was just a number picked out at random by me for
clarification of my question.
So you wouldn't want to share your 'sweet' findings, would you??
thanks!

I had a dig around through a few thousand spreadsheets... and found it.

9.05m, 12.6m, 18.3m, 26.4m, 33.3m, 44.9m.

If you want to cover 60m, leave the 26.4 out of the list.

Did someone mention 60' (18.3m), it is in the list, but it is more
critical than 26.4 or 12.6.

As noted in my earlier post, if you want to be 10% or more away from n
half waves on all bands, there is no solution.

These calcs don't consider proximity of objects that may shift the
tuning.

My advice still stands that the higher order parallel resonances aren't
such an issue, so this method unnecessarily constrains the solution..

Owen

Hey, I'm just learning and absorbing so anything new is a place for me to
start. Thanks again!
woody

"Owen Duffy" wrote in message
...
"Woody" wrote in news:hYdli.29709$BT3.8034@trnddc06:

Hi Owen. 5% was just a number picked out at random by me for
clarification of my question.
So you wouldn't want to share your 'sweet' findings, would you??
thanks!

I had a dig around through a few thousand spreadsheets... and found it.

9.05m, 12.6m, 18.3m, 26.4m, 33.3m, 44.9m.

If you want to cover 60m, leave the 26.4 out of the list.

Did someone mention 60' (18.3m), it is in the list, but it is more
critical than 26.4 or 12.6.

As noted in my earlier post, if you want to be 10% or more away from n
half waves on all bands, there is no solution.

These calcs don't consider proximity of objects that may shift the
tuning.

My advice still stands that the higher order parallel resonances aren't
such an issue, so this method unnecessarily constrains the solution..

Owen

In article ,
Owen Duffy wrote:

A simple program or spreadsheet ought to be able to do the necessary
calculations... try every wire length from 66 feet to 132 feet and see
if you can find a length which is a comfortable percentage away from
an even multiple of 1/2 wavelength on each frequency. Or,

You probably mean't any integral multiple of a half wave.

You're right... integral multiple of a half-wavelength, or even
multiples of a quarter-wavelength are two alternative ways for stating
the lengths to be avoided (high feedpoint Z).

alternatively, iterate through each frequency, calculate the
1/2-wavelength multiples, and "blacklist" every possible length which
is too close to these multiples.

I have done just that, and searched for "sweet" wire lengths that aren't
within say 5% of band edge for all HF bands. It sounds like a solution to
the problem doesn't it. (5% implies that you have a pretty determinate
scenario, which is a big assumption. IIRC 10%+ will not give a practical
result on the higher bands.)

Problem is that it probably unecessarily constrains the solution.

Entirely possible!

The input impedance and the feed point voltage of an end fed wire at its
higher parallel resonances falls, so that whilst you might want to avoid
the first such resonance, the impedance (and feed point voltage) at the
third or higher resonance might well be low enough to not worry about it.

And, even if it was a bit high, you might not need to be more than a
couple of percent away from it to get it down to a length that might
work.

Odds are that some amount of experimentation is going to be required,
at any given installation, to find a wire length which tunes up well
with these ATUs. The orientation of the wire (vertical, inverted-L,
etc.), height about ground, presence of trees and metallic objects,
and (perhaps most importantly) the details of the ATU's grounding
system, are likely to change the impedances around enough to make the
"textbook" answers less than completely effective.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:
In article t3ali.3392$Y_3.570@trnddc04, Woody wrote:


Well.. a million thanks for that. Quite a cool history lesson as well. So
now I'm looking for an SEA tuner... LOL...

Listen, that all makes perfect sense but just to clarify, a.) now I know why
that triton did so poorly when tested. We calc'd 1/2 wavelength for the
longwire, and b.) Again, for continuity and clarity of this thread for
future surfers...... what then, considering our discussed auto-tuners, would
be the optimal length for a longwire that would be used for amateur/MARS,
3-30MHz?
Pick 1/2wavelength on say 2.8Mhz and just cut it? Or calc 1/2wavelength on
the lowest and add 5% or some arbitrary odd number??
Which plan will offer the least chance of dropping a 1/2wl further up the
band on a desired frequency?


I think you'll need to run a a simple calculation, based on the
frequencies you actually want to use.

What you'll want, is a wire whose length is not particularly close to
any multiple of 1/2 wavelength, on any frequency you want to use. A
wire which would match easily on 80 meters (e.g. 1/4 wavelength long)
would be a bad choice if you want to work on 40 meters as well, as
it'd be 1/2 wavelength long.

A simple program or spreadsheet ought to be able to do the necessary
calculations... try every wire length from 66 feet to 132 feet and see
if you can find a length which is a comfortable percentage away from
an even multiple of 1/2 wavelength on each frequency. Or,
alternatively, iterate through each frequency, calculate the
1/2-wavelength multiples, and "blacklist" every possible length which
is too close to these multiples.

For what it's worth, SGC sells a longwire antenna 60' in length, which
they say works well on both lower and higher HF bands. It might or
might not be a good choice for MARS frequencies.


The other strategy is to use two wires of appropriately different
lengths connected together at the feedpoint. (the SGC whips do this, for
instance).. Space the wires some distance apart (a few inches would
do).. What this does is put multiple bumps in the impedance curve and
eliminates the pathological cases where you have very high Z when the
(one) wire is a half wavelength or multiple thereof. At those
frequencies where one wire *is* a half wavelength, and presents a high
Z, the other one is likely NOT a multiple of a half wavelength, and so,
will present a reasonable impedance. Sure, they interact (as folks
making multiband dipoles find when trying to cut and trim), but all that
really does is shift the resonances around.

An interesting question would be what is the optimum ratio of lengths..
probably something like 1:1.618 or 1:2.7183

In article t3ali.3392$Y_3.570@trnddc04, "Woody"
wrote:

Well.. a million thanks for that. Quite a cool history lesson as well. So
now I'm looking for an SEA tuner... LOL...

Listen, that all makes perfect sense but just to clarify, a.) now I know why
that triton did so poorly when tested. We calc'd 1/2 wavelength for the
longwire, and b.) Again, for continuity and clarity of this thread for
future surfers...... what then, considering our discussed auto-tuners, would
be the optimal length for a longwire that would be used for amateur/MARS,
3-30MHz?
Pick 1/2wavelength on say 2.8Mhz and just cut it? Or calc 1/2wavelength on
the lowest and add 5% or some arbitrary odd number??
Which plan will offer the least chance of dropping a 1/2wl further up the
band on a desired frequency?
thanks,
Woody


What we did, is to try and have a Longwire with a 1/4 Wave Point near
the lowest Operating Frequency like for the 2006Khz Alaska Private
Fixed Frequency, then calculate the Natural 1/2 Wave Point for that
Wire, then adjust the 1/4 Wave Length, SHORTER, until the 1/2 Wave Point
DeadBand (2.5% or so) was in a part of the speectrum the Station wasn't
Licensed for, Marine and Alaska Private Fixed have specific Channels,
and Bands in the MF/HF Spectrum, and it isn't to hard to move the
DeadBand to a nonused portion of the Spectrum. For the HAMS, that want
a "Do everything, cover the whole Dc to Light Spectrum, with one
Longwire Tunter", the answer is "Design and Build your own Dam Tuner
with an integrate Longwire Switch and put up Multiple lengths of wire",
because there isn't a product out there, that I am aware, of that does
this, YET....

Bruce in alaska
--
add a 2 before @